Francisco Geu Flores | University of Duisburg-Essen (original) (raw)
Papers by Francisco Geu Flores
International Journal of Computer Science in Sport, 2019
Even several years after total hip (THR) and total knee replacement (TKR) surgery patients freque... more Even several years after total hip (THR) and total knee replacement (TKR) surgery patients frequently show deficient gait patterns leading to overloads and relieving postures on the contralateral side or in the spine. Gait training is, in these cases, an essential part of rehabilitation. The aim of this study was to compare different feedback methods during gait training after THR and TKR focusing, in particular, on auditory feedback via sonification. A total of 240 patients after THR and TKR were tested in a pre-post-test design during a 3-week rehabilitation period. Even though sonification did not show, statistically, a clear advantage over other feedback methods, it was well accepted by the patients and seemed to significantly change gait pattern during training. A sudden absence of sonification during training led to a rapid relapse into previous movement patterns, which highlights its effectiveness in breaking highly automated gait patterns. A frequent use of sonification duri...
International Orthopaedics
Purpose Orthopaedic scores are essential for the clinical assessment of movement disorders but re... more Purpose Orthopaedic scores are essential for the clinical assessment of movement disorders but require an experienced clinician for the manual scoring. Wearable systems are taking root in the medical field and offer a possibility for the convenient collection of motion tracking data. The purpose of this work is to demonstrate the feasibility of automated orthopaedic scorings based on motion tracking data using the Harris Hip Score and the Knee Society Score as examples. Methods Seventy-eight patients received a clinical examination and an instrumental gait analysis after hip or knee arthroplasty. Seven hundred forty-four gait features were extracted from each patient’s representative gait cycle. For each score, a hierarchical multiple regression analysis was conducted with a subsequent tenfold cross-validation. A data split of 70%/30% was applied for training/testing. Results Both scores can be reproduced with excellent coefficients of determination R2 for training, testing and cros...
Water slide manufacturers are constantly searching for innovative designs that maximize the rider... more Water slide manufacturers are constantly searching for innovative designs that maximize the rider’s fun while complying with safety requirements. However, the current state-of-the-art does not offer any simulation tool capable of aiding the design phase before manufacture in an affordable computational time. This paper presents a novel approach using smooth surface models together with Saint Venant’s filament theory to predict the water channel and by this a realistic estimation of passenger - waterslide interaction. The model is applied to circular slide cross sections but can be extended to general surfaces. The paper covers the theory and the experimental validation. It is shown that the predicted water channel follows very well the measurement, and that the Saint Venant’s terms taking into consideration water channel heights and deformation of water cross-section play a marginal role and thus can be neglected, allowing one to use a simple Bernoulli filament model with proper wat...
Physical Medicine and Rehabilitation Research
Background and Objective: During the action of sitting, up to 35% of the patients push to the aff... more Background and Objective: During the action of sitting, up to 35% of the patients push to the affected side after an acute hemispheric stroke. We analyse the deviation of the upper trunk to the affected side (DUTAS) during walking in patients having recovered from a hemispheric stroke and demonstrate the negative impact of DUTAS on gait performance. Methods: In 99 patients having recovered after a hemispheric stroke (mean age: 58yrs) with more than 10-meter walking ability, kinematics (during walking at the preferred gait speed) were recorded using an array of 8 VICON cameras. Reflective markers were attached to the body, especially at the sacrum and C7 cervical vertebra. The deviation angle of the vertical from the line through the sacrum and C7-marker was measured. Walking abnormalities, including the abnormal posture of the upper trunk, were rated by five rehabilitation experts. Results: Relevant DUTAS was observed in 35.6% of the right-side, and 37% of the left-side affected patients. There was a highly significant (p<.0001) positive correlation between rating of gait abnormalities and DUTAS and a significant (p<.01) negative correlation between DUTAS to the right or left side and gait speed. Additionally, the post-stroke period (shorter than four months or longer than 4 up to 120 months) had no influence on DUTAS. Conclusions: The lateral deviation of the upper trunk to the affected side during walking is frequently observed in post-stroke patients. Because of the associated negative impact on gait performance, correction of trunk lateral bending is essential in post-stroke gait rehabilitation.
2022 19th European Radar Conference (EuRAD)
Kurzfassung des Tagungsbeitrags.
Material for self-study of the Stroke Mobility Score (SMS)<br>
Blank form of the Stroke Mobility Score (SMS)<br>
Advances in Mechanism and Machine Science, 2019
This paper describes a new method for modeling the dynamics of rolling rigid-bodies in the framew... more This paper describes a new method for modeling the dynamics of rolling rigid-bodies in the framework of object-oriented multibody dynamics with minimal coordinates. The method consists in modeling each rigid-body surface as a kinetostatic transmission element mapping the motion of the rigid-body as well as a two-parametric relative motion on its surface to the spatial motion of a corresponding Darboux frame. This allows for contact constraints to be handled as a subset of the closure conditions of a kinematical chain at position level and, hence, to be assembled into a multibody framework without further efforts. Furthermore, the paper shows two examples which use surface-fitting with bivariate B-Splines to define the surface joints, and discusses the advantages of solving the contact equations at position level.
Kurzfassung des Tagungsbeitrags.
For large robot-base displacements, for instance caused by short and long crested waves on a vess... more For large robot-base displacements, for instance caused by short and long crested waves on a vessel, large vertical displacements at the robot end-effector with respect to the base are expected
ROMANSY 22 – Robot Design, Dynamics and Control, 2018
This paper describes a generalization of the virtual redundant axis (VRA) method previously intro... more This paper describes a generalization of the virtual redundant axis (VRA) method previously introduced by the authors for robust, position-controlled inverse kinematics of serial robots passing through or close to a singular configuration. While the VRA method regards only one body- or inertially-fixed virtual axis, the new approach can handle multiple “floating” virtual axes which are smooth functions of the robot configuration and are not necessarily fixed to the robot links or base. This allows for robustly negotiating inverse kinematics even in the presence of multiple singularities with a single parameter set, while concentrating tracking errors solely in the locked directions. The paper discusses the theory, including a novel Jacobian form with non body-fixed joint axes, validating its performance on a real industrial robot Kuka KR15/2 and comparing it to the weighted damped least squares method (WDLS).
Medical Science Monitor, 2020
Background: For future development of machine learning tools for gait impairment assessment after... more Background: For future development of machine learning tools for gait impairment assessment after stroke, simple observational whole-body clinical scales are required. Current observational scales regard either only leg movement or discrete overall parameters, neglecting dysfunctions in the trunk and arms. The purpose of this study was to introduce a new multiple-cue observational scale, called the stroke mobility score (SMS). Material/Methods: In a group of 131 patients, we developed a 1-page manual involving 6 subscores by Delphi method using the video-based SMS: trunk posture, leg movement of the most affected side, arm movement of the most affected side, walking speed, gait fluency and stability/risk of falling. Six medical raters then validated the SMS on a sample of 60 additional stroke patients. Conventional scales (NIHSS, Timed-Up-And-Go-Test, 10-Meter-Walk-Test, Berg Balance Scale, FIM-Item L, Barthel Index) were also applied. Results: (1) High consistency and excellent inter-rater reliability of the SMS were verified (Cronbach's alpha >0.9). (2) The SMS subscores are non-redundant and reveal much more nuanced whole-body dysfunction details than conventional scores, although evident correlations as e.g. between 10-Meter-Walk-Test and subscore "gait speed" are verified. (3) The analysis of cross-correlations between SMS subscores unveils new functional interrelationships for stroke profiling. Conclusions: The SMS proves to be an easy-to-use, tele-applicable, robust, consistent, reliable, and nuanced functional scale of gait impairments after stroke. Due to its sensitivity to whole-body motion criteria, it is ideally suited for machine learning algorithms and for development of new therapy strategies based on instrumented gait analysis.
CISM International Centre for Mechanical Sciences, 2016
Several techniques have been developed in the past to handle the inverse kinematics of serial rob... more Several techniques have been developed in the past to handle the inverse kinematics of serial robots passing through or close to singular configurations. As a common line, these approaches operate at velocity level, seeking a trade-off between tracking accuracy and joint velocity feasibility. While providing robust control, some difficulties arise in these methods for predicting end-effector errors and their spread in SE(3). In a previous paper, the virtual redundant axis (VRA) method was introduced at velocity level, by which end-effector velocity errors could be concentrated in non-controllable directions. The present paper extends the VRA method to position level, allowing for a precise motion tracking and the handling of singularity paths in the same way as regular motions.
This paper describes a new method for robot hand wrist singularity avoidance by using a virtual r... more This paper describes a new method for robot hand wrist singularity avoidance by using a virtual redundant axis. The method is described for the application of large spatial robot base motion compensation for a 6 degrees of freedom serial manipulator using an inertial measurement unit such that the end effector maintains a prescribed target location. The overall system is tested for a KUKA KR500 system and computer-generated as well as real wave signals with large amplitudes.
Mechanisms, Transmissions and Applications, 2015
ABSTRACT Drive simulators using serial robots, such as the KUKA robot “Robocoaster”, are becoming... more ABSTRACT Drive simulators using serial robots, such as the KUKA robot “Robocoaster”, are becoming attractive for situations in which the workspace of traditional Stewart platforms is not suited to accommodate large target rotations, allowing for a wider range of possibilities. Nevertheless—even when using serial robots—the exact target motion can often not be exactly reproduced. In these cases, motion cueing algorithms (MCA) are used to produce a motion which feels as realistic as possible while remaining in the robot acceleration workspace. This paper analyzes the numerical properties of all currently existing MCA (classical, adaptive, optimal, and model predictive control) and selects the most suitable MCA using objective criteria. It also introduces a new procedure for tuning the optimal MCA such that it behaves as good as and even better than much more involved techniques based on the model predictive control (MPC). The new algorithm, termed ZyRo-K, shows best properties for reproducing the desired linear specific force while reducing the rotational false cues. While the work shown in this paper is restricted to numerical evaluation using state-of-the-art “goodness” metrics, the application and test of the algorithms for human passengers on a Robocoaster is currently being prepared and will be published in the near future.
Mechanisms and Machine Science, 2013
ABSTRACT This paper presents a direct solution approach for the so-called general waiter motion p... more ABSTRACT This paper presents a direct solution approach for the so-called general waiter motion problem, which consists in moving a tablet as fast as possible from one pose to the other such that non of the objects resting on the tablet slides at any time. The question is akin to several industrial problems in which tangential forces are restricted due to functional reasons, such as suction grippers, motion of sensitive goods, etc. In contrast to existing approaches which parametrize the problem in configuration (joint) space, we decompose the overall task into two cascaded main components: shaping the optimal geometry of the spatial path, and finding the time optimal one-dimensional motion of the system along this path. The spatial path is parametrized using via poses in SE(3), making it possible to reduce the search space to significant physical subspaces, and to interact intuitively with the user. The overall optimization is subdivided into a series of subproblems with cost functions and search spaces of increasing fineness, such that each subproblem can be solved with the output of its predecessor. A solution of the waiter motion problem with four objects illustrates the applicability of the algorithm.
International Journal of Computer Science in Sport, 2019
Even several years after total hip (THR) and total knee replacement (TKR) surgery patients freque... more Even several years after total hip (THR) and total knee replacement (TKR) surgery patients frequently show deficient gait patterns leading to overloads and relieving postures on the contralateral side or in the spine. Gait training is, in these cases, an essential part of rehabilitation. The aim of this study was to compare different feedback methods during gait training after THR and TKR focusing, in particular, on auditory feedback via sonification. A total of 240 patients after THR and TKR were tested in a pre-post-test design during a 3-week rehabilitation period. Even though sonification did not show, statistically, a clear advantage over other feedback methods, it was well accepted by the patients and seemed to significantly change gait pattern during training. A sudden absence of sonification during training led to a rapid relapse into previous movement patterns, which highlights its effectiveness in breaking highly automated gait patterns. A frequent use of sonification duri...
International Orthopaedics
Purpose Orthopaedic scores are essential for the clinical assessment of movement disorders but re... more Purpose Orthopaedic scores are essential for the clinical assessment of movement disorders but require an experienced clinician for the manual scoring. Wearable systems are taking root in the medical field and offer a possibility for the convenient collection of motion tracking data. The purpose of this work is to demonstrate the feasibility of automated orthopaedic scorings based on motion tracking data using the Harris Hip Score and the Knee Society Score as examples. Methods Seventy-eight patients received a clinical examination and an instrumental gait analysis after hip or knee arthroplasty. Seven hundred forty-four gait features were extracted from each patient’s representative gait cycle. For each score, a hierarchical multiple regression analysis was conducted with a subsequent tenfold cross-validation. A data split of 70%/30% was applied for training/testing. Results Both scores can be reproduced with excellent coefficients of determination R2 for training, testing and cros...
Water slide manufacturers are constantly searching for innovative designs that maximize the rider... more Water slide manufacturers are constantly searching for innovative designs that maximize the rider’s fun while complying with safety requirements. However, the current state-of-the-art does not offer any simulation tool capable of aiding the design phase before manufacture in an affordable computational time. This paper presents a novel approach using smooth surface models together with Saint Venant’s filament theory to predict the water channel and by this a realistic estimation of passenger - waterslide interaction. The model is applied to circular slide cross sections but can be extended to general surfaces. The paper covers the theory and the experimental validation. It is shown that the predicted water channel follows very well the measurement, and that the Saint Venant’s terms taking into consideration water channel heights and deformation of water cross-section play a marginal role and thus can be neglected, allowing one to use a simple Bernoulli filament model with proper wat...
Physical Medicine and Rehabilitation Research
Background and Objective: During the action of sitting, up to 35% of the patients push to the aff... more Background and Objective: During the action of sitting, up to 35% of the patients push to the affected side after an acute hemispheric stroke. We analyse the deviation of the upper trunk to the affected side (DUTAS) during walking in patients having recovered from a hemispheric stroke and demonstrate the negative impact of DUTAS on gait performance. Methods: In 99 patients having recovered after a hemispheric stroke (mean age: 58yrs) with more than 10-meter walking ability, kinematics (during walking at the preferred gait speed) were recorded using an array of 8 VICON cameras. Reflective markers were attached to the body, especially at the sacrum and C7 cervical vertebra. The deviation angle of the vertical from the line through the sacrum and C7-marker was measured. Walking abnormalities, including the abnormal posture of the upper trunk, were rated by five rehabilitation experts. Results: Relevant DUTAS was observed in 35.6% of the right-side, and 37% of the left-side affected patients. There was a highly significant (p<.0001) positive correlation between rating of gait abnormalities and DUTAS and a significant (p<.01) negative correlation between DUTAS to the right or left side and gait speed. Additionally, the post-stroke period (shorter than four months or longer than 4 up to 120 months) had no influence on DUTAS. Conclusions: The lateral deviation of the upper trunk to the affected side during walking is frequently observed in post-stroke patients. Because of the associated negative impact on gait performance, correction of trunk lateral bending is essential in post-stroke gait rehabilitation.
2022 19th European Radar Conference (EuRAD)
Kurzfassung des Tagungsbeitrags.
Material for self-study of the Stroke Mobility Score (SMS)<br>
Blank form of the Stroke Mobility Score (SMS)<br>
Advances in Mechanism and Machine Science, 2019
This paper describes a new method for modeling the dynamics of rolling rigid-bodies in the framew... more This paper describes a new method for modeling the dynamics of rolling rigid-bodies in the framework of object-oriented multibody dynamics with minimal coordinates. The method consists in modeling each rigid-body surface as a kinetostatic transmission element mapping the motion of the rigid-body as well as a two-parametric relative motion on its surface to the spatial motion of a corresponding Darboux frame. This allows for contact constraints to be handled as a subset of the closure conditions of a kinematical chain at position level and, hence, to be assembled into a multibody framework without further efforts. Furthermore, the paper shows two examples which use surface-fitting with bivariate B-Splines to define the surface joints, and discusses the advantages of solving the contact equations at position level.
Kurzfassung des Tagungsbeitrags.
For large robot-base displacements, for instance caused by short and long crested waves on a vess... more For large robot-base displacements, for instance caused by short and long crested waves on a vessel, large vertical displacements at the robot end-effector with respect to the base are expected
ROMANSY 22 – Robot Design, Dynamics and Control, 2018
This paper describes a generalization of the virtual redundant axis (VRA) method previously intro... more This paper describes a generalization of the virtual redundant axis (VRA) method previously introduced by the authors for robust, position-controlled inverse kinematics of serial robots passing through or close to a singular configuration. While the VRA method regards only one body- or inertially-fixed virtual axis, the new approach can handle multiple “floating” virtual axes which are smooth functions of the robot configuration and are not necessarily fixed to the robot links or base. This allows for robustly negotiating inverse kinematics even in the presence of multiple singularities with a single parameter set, while concentrating tracking errors solely in the locked directions. The paper discusses the theory, including a novel Jacobian form with non body-fixed joint axes, validating its performance on a real industrial robot Kuka KR15/2 and comparing it to the weighted damped least squares method (WDLS).
Medical Science Monitor, 2020
Background: For future development of machine learning tools for gait impairment assessment after... more Background: For future development of machine learning tools for gait impairment assessment after stroke, simple observational whole-body clinical scales are required. Current observational scales regard either only leg movement or discrete overall parameters, neglecting dysfunctions in the trunk and arms. The purpose of this study was to introduce a new multiple-cue observational scale, called the stroke mobility score (SMS). Material/Methods: In a group of 131 patients, we developed a 1-page manual involving 6 subscores by Delphi method using the video-based SMS: trunk posture, leg movement of the most affected side, arm movement of the most affected side, walking speed, gait fluency and stability/risk of falling. Six medical raters then validated the SMS on a sample of 60 additional stroke patients. Conventional scales (NIHSS, Timed-Up-And-Go-Test, 10-Meter-Walk-Test, Berg Balance Scale, FIM-Item L, Barthel Index) were also applied. Results: (1) High consistency and excellent inter-rater reliability of the SMS were verified (Cronbach's alpha >0.9). (2) The SMS subscores are non-redundant and reveal much more nuanced whole-body dysfunction details than conventional scores, although evident correlations as e.g. between 10-Meter-Walk-Test and subscore "gait speed" are verified. (3) The analysis of cross-correlations between SMS subscores unveils new functional interrelationships for stroke profiling. Conclusions: The SMS proves to be an easy-to-use, tele-applicable, robust, consistent, reliable, and nuanced functional scale of gait impairments after stroke. Due to its sensitivity to whole-body motion criteria, it is ideally suited for machine learning algorithms and for development of new therapy strategies based on instrumented gait analysis.
CISM International Centre for Mechanical Sciences, 2016
Several techniques have been developed in the past to handle the inverse kinematics of serial rob... more Several techniques have been developed in the past to handle the inverse kinematics of serial robots passing through or close to singular configurations. As a common line, these approaches operate at velocity level, seeking a trade-off between tracking accuracy and joint velocity feasibility. While providing robust control, some difficulties arise in these methods for predicting end-effector errors and their spread in SE(3). In a previous paper, the virtual redundant axis (VRA) method was introduced at velocity level, by which end-effector velocity errors could be concentrated in non-controllable directions. The present paper extends the VRA method to position level, allowing for a precise motion tracking and the handling of singularity paths in the same way as regular motions.
This paper describes a new method for robot hand wrist singularity avoidance by using a virtual r... more This paper describes a new method for robot hand wrist singularity avoidance by using a virtual redundant axis. The method is described for the application of large spatial robot base motion compensation for a 6 degrees of freedom serial manipulator using an inertial measurement unit such that the end effector maintains a prescribed target location. The overall system is tested for a KUKA KR500 system and computer-generated as well as real wave signals with large amplitudes.
Mechanisms, Transmissions and Applications, 2015
ABSTRACT Drive simulators using serial robots, such as the KUKA robot “Robocoaster”, are becoming... more ABSTRACT Drive simulators using serial robots, such as the KUKA robot “Robocoaster”, are becoming attractive for situations in which the workspace of traditional Stewart platforms is not suited to accommodate large target rotations, allowing for a wider range of possibilities. Nevertheless—even when using serial robots—the exact target motion can often not be exactly reproduced. In these cases, motion cueing algorithms (MCA) are used to produce a motion which feels as realistic as possible while remaining in the robot acceleration workspace. This paper analyzes the numerical properties of all currently existing MCA (classical, adaptive, optimal, and model predictive control) and selects the most suitable MCA using objective criteria. It also introduces a new procedure for tuning the optimal MCA such that it behaves as good as and even better than much more involved techniques based on the model predictive control (MPC). The new algorithm, termed ZyRo-K, shows best properties for reproducing the desired linear specific force while reducing the rotational false cues. While the work shown in this paper is restricted to numerical evaluation using state-of-the-art “goodness” metrics, the application and test of the algorithms for human passengers on a Robocoaster is currently being prepared and will be published in the near future.
Mechanisms and Machine Science, 2013
ABSTRACT This paper presents a direct solution approach for the so-called general waiter motion p... more ABSTRACT This paper presents a direct solution approach for the so-called general waiter motion problem, which consists in moving a tablet as fast as possible from one pose to the other such that non of the objects resting on the tablet slides at any time. The question is akin to several industrial problems in which tangential forces are restricted due to functional reasons, such as suction grippers, motion of sensitive goods, etc. In contrast to existing approaches which parametrize the problem in configuration (joint) space, we decompose the overall task into two cascaded main components: shaping the optimal geometry of the spatial path, and finding the time optimal one-dimensional motion of the system along this path. The spatial path is parametrized using via poses in SE(3), making it possible to reduce the search space to significant physical subspaces, and to interact intuitively with the user. The overall optimization is subdivided into a series of subproblems with cost functions and search spaces of increasing fineness, such that each subproblem can be solved with the output of its predecessor. A solution of the waiter motion problem with four objects illustrates the applicability of the algorithm.